Multi-touch enabled devices are known in the art. A multi-touch enabled device is a device that can sense multiple touches at the same time. Thus, a multi-touch enabled device can, for example, sense two touch events that take place simultaneously at two different positions on a multi-touch panel and are caused by two fingers being pressed down on the panel. Examples of multi-touch enabled devices are discussed in U.S. patent application Ser. No. 11/649,998, entitled “Proximity and Multi-Touch Sensor Detection and Demodulation,” filed on Jan. 3, 2007 and hereby incorporated by reference in its entirety. Multi-point enabled devices define a more general set of devices that include multi-touch enabled devices as well as similar devices such as the multi-proximity sensor devices discussed in U.S. patent application Ser. No. 11/649,998 mentioned above.
While the benefits of multi-touch enabled interfaces are known, these devices can present some interface design challenges. Existing interface design conventions have assumed a single pointing user input device that specifies a single location at a time. Examples include a mouse or a touch pad.
More specifically, many existing graphical user interface (GUI) systems provide user interfaces in which various portions of a display are associated with separate software elements. Thus, for example, portions of a display can be associated with a window, and the window can be associated with a specific software application and/or process. A mouse can be used to interact with the window and the application or process associated with that window. The mouse cursor can then be moved to another window to interact with another application or process. Because only a single pointing device is used, interaction with only a single window and application or process can occur at a time.
The assumption of a single interaction with a window at any one time can greatly simplify user interface design. The application and/or process running within a window can operate under the assumption that a detected interaction with that particular window is the only input being received. Thus, the application and/or process need not concern itself with the possibility of other user interactions occurring in other portions of the display outside that window. Furthermore, a window can be additionally partitioned into various elements, wherein each element is associated with a specific portion of the window. Each element can be implemented by a separate software element (e.g., a software object). Again, each software object can process interactions that occur in its associated area without concerning itself with interactions that may be simultaneously occurring elsewhere.
On the other hand, if a multi-touch interface is being used, two or more touch events can simultaneously occur at different portions of the display. This can make it difficult to split the display into different portions and have different independent software elements process interactions associated with each portion. Furthermore, even if the display is split up into different portions, multiple touch events can occur in a single portion. Therefore, a single application, process or other software element may need to process multiple simultaneous touch events. However, if each application, process or other software element needs to consider multiple touch interactions, then the overall cost and complexity of software running at the multi-touch enabled device may be undesirably high. More specifically, each application may need to process large amounts of incoming touch data. This can require high complexity in applications of seemingly simple functionality, and can make programming for a multi-touch enabled device generally difficult and expensive. Also, existing software that assumes a single pointing device can be very difficult to convert or port to a version that can operate on a multi-point or a multi-touch enabled device.